The collapse of Spirit Airlines and the potenital loss of 17,000 jobs is not an isolated failure. It is a warning signal. An 80% surge in jet fuel prices, trimming of global airline capacity, and an average 12% rise in global airfares have disrupted the low-cost airline model. Is this the beginning of the end for ultra‑cheap tickets or a temporary stress test before conditions normalise? The answers lie in a few key variables now shaping airlines.